JD 300 Industrial Tractor smokes when started

[tlfarm]

I have a JD300 Industrial tractor and when I start it it skips and black smoke comes out of the muffler until it warms up a little. I have put a new float and carb kit on it. I installed a shut off valve on the fuel line and as long as I shut the valve off after use it is fine. Does anyone have an idea of what is causing the problem??

 

[strum456]

I am not knowledgable on john deeres, but generally speaking, Id say your float valve is leaking, which over fills the float boul and carb when the tractor sits. Floats can be a real pita. Check float height, seat and needle condition, and for contact between the float and the carb. Look for any rub marks on the float first. Sometimes I coat the float with a light film of grease and put it in and rattle it around. Then take it back apart and look for contact.